May not be too much pre-pounce
I notice that when the idle is high, 78 will squat a GOOD 2-3 inches. I even notice the nose come up a bit when it squats. That indicates to me, that the rear must be lowering quite a bit for me to notice the nose coming up that significantly.
Now, when the idle is not high, the squat is not as deep, because there is less power at the lower rpm's to transfer to the rear end and half-shafts. I still notice it 'set down' a bit, but not like when it is cold out and the engine hasn't warmed up completely.
If your previous vette was a warm-weather vette, and well maintained (with little to no high idle conditions) you may not have experienced the deep lowering of the rear end. Plus, you say it's been a while since you've driven a shark.
Usually, stories grow with the telling, but sometimes they also diminish in our memories and the truth becomes forgotten. I am in no way a mechanic, but in logically thinking of how the rear is put together, I don't feel the leaf springs or shocks would have anything to do with how the vette handles taking the power load from the engine to the rear wheels. That is strictly a drive train funtion. I think it is the movement of the half shafts between the rear end and the wheels that cause the vette to lower like that.
Maybe the trailing arm bushings being missing would cause the vehicle to lower even more? I don't know. Take it for another drive, just for fun!
btw, a clam will take anything you throw at it and give you back a pearl. Sort of like an 'awful' twisty road being thrown at the vette and being given a great drive!
Silver